Process for making metallic-coated membrane



Patented May 19,. 1936 UNITED STATES PATENT OFFICE 2,041,297 PROCESS FOR MAKING METALLIC-COATED MEMBRANE Robson S. Moore,

Columbia Ribbon Great Neck, N. Y., assignor to a: Carbon Manufacturing Company, Glen Cove, N. Y.

No Drawing. Application June 18, 1935, Serial No. 27,185

2 Claims. (CI. 91-10) characteristics such as strength, toughness and waterproofness. The objects of my invention are to produce these desirable characteristics in a product suitable for use in place of metal foil or other membraneous material for many purposes such as the wrapping of tobacco products,confectionary and other merchandise.

.I am aware that membraneous materials, such as paper, have been and are being manufactured by a varietyof processes, which have a coating of metallic powders upon their surface, and that there are composite papers, consisting of a layer of metal foil attached adhesively to the paper is a matter of common knowledge. All of these products have drawbacks and disadvantages which have prevented their general adoption and use to as large an extent as they would otherwise have attained. These disadvantages are overcome in large degree by my invention.

In brief, my invention consists in a method of coating'membranes, as for example, paper, by combining in liquid form, by means of heat, on the surface thereof, two or more component ingredients of a coating applied thereto, one of which ingredients is a metallic powder and another is a resinous, fatty or waxy substance, which is converted to a liquid state on the surface of the paper under the influence of heat. Other ingredients may also be present in minor amounts for the purpose'of modifying or controlling one or more physical characteristics of the coating.

Inthe methods heretofore employed, the metallic powder has usually been mixed with various liquid binders or vehicles, the mixture applied in liquid or semi-liquid form to the surface of the membrane by various means and allowed to dry or harden on the surface. In some cases, heat has been used to slightly soften the coating or to render it more adhesive to the powder. The result has been that the particles of metallic powder which are in the form of minute and very thin scales of the metal, have been left upon deposition in a helter-skelter arrangement without any semblance of order in their placement. Such coatings lack smoothness, high gloss and opacity, and do not effectively resist the penetration of moisture therethrough. The appearance and smoothness of such coatings are improved by calendering the surface between highly polished rolls but the resultant product lacks the highly desirable qualities of the product resulting from the practice of my invention, for the reasons hereinafter explained.

In the practice of my invention, when the membrane I am coating is paper, I prefer to use a' paper which possesses a low absorption factor, that is, either a-paper the surface of which has been treated with a material which fills the pores thereof or one which has been highly calendered to close the pores and so render the surface of the paper dense and relatively non-absorbent. To this paper I apply a layer of rosin, wax or gum, or a combination of them, which melts to a liquid under the influence of heat. For this layer I prefer to use a resinous gum having a high melting point, that is, over 220 F. or above the boiling point of water. I prefer also to use a gum or wax or a mixture of them which, when melted, forms a free flowing fluid since the desirable qualities of the product are attained by reason of the fluidity of this coating when in a molten state. Upon this layer I apply a thin layer or coating of metallic powder either in mixture with a liquid or semi-liquid vehicle or as a heat to the membrane sufi'icient to melt the under coating .to a liquid state. In this condition the minute scales of metal on the surface of the coating settle down and float into position in the liquefied under coating and produce an exceptionally smooth and brilliant surface with the scales of metal virtually parallel to each other and virtually in contact one with another instead of in the helter-skelter positions which they occupied before the fusible layer was converted to a liquid by the application of heat thereto. This rearrangement of the metallic scales from the haphazard to the orderly takes place almost instantly upon the melting to a liquid of the undercoating and it continues for an appreciable length of time thereafter, several seconds while the coating is kept in a liquid state. Before applying heat to melt the under coating, the thin scales of metal lie on the surface of the under coating in an infinite variety of positions, some on edge, some fiat and others at every conceivable angle therebetween. Such a coating has the appearance of frosted metal. It has a metallic appearance but not brilliance. It is necessary to calender or burnish such a surface to give it a brilliant lustre.

Nor is such a coating, in which the scales of metal stand in such helter-skelter fashion as opaque as is a coating produced by-my method, for the reason that the binding materials used to retain the metallic scales on the surface of the membrane are translucent-and permit the passage of light between the scales when they are arranged in a helter-skelter fashion. But when the scales are laid fiat and interlocking and overlapping in parallel positions the passage of light is effectively cut off.

After the same manner, the imperviousness of dry powder by well known means. I then apply metal surface to one the coating to moisture is greatly improved by the rearrangement skelter arrangement to the overlapping interlocking parallel arrangement which is brought about by converting the under coating from a solid to a liquid state by fusion.

In addition to these advantages, I find that the liquefying of the undercoating, if continued for a few seconds, greatly improves the uniformity of distribution of the metallic scales when the original distribution is non-uniform. Thus a coating of metal powder which is streaked or imperfectly distributed becomes more evenly distributed when the under coating is maintained in a liquid state for an appreciable length of time. Why this is so is not entirely evident but I flnd it to be a fact. Thus my method is found to materially improve the distribution of the metallic scales even after they have been applied.

Thus the fusion of the undercoating to a free flowing non-viscous liquid performs four important functions, namely, it alters the appearance of the metallic coating from that of a frosted of high gloss and lustre, it renders the coating more opaque to light, it increases its resistance to the passage of moisture, and improves the distribution of the metallic scales throughout the coating.

The purpose of the non-absorbent surface of the paper is to prevent the rapid absorption of the resinous or waxy coating substance when it is in the liquid state while heated, and to conserve the quantity of coating required. When a more absorbent paper or membrane is used, a reater quantity of coating substance is required.

I have described a preferred form of the method of practicing my invention but there are variants therefrom and other methods which fall Within the scope of the invention. For example, I may apply the first coating of resinous or waxy material in such a condition that its surface is lightly sticky or tacky and I may dust onto such surface a dry metallic powder and then remove the surplus powder which does not adhere to the undercoating.

I then heat the thus coated membrane by passing over a heated roll with the uncoated side of the membrane in contact with the surface of the heated roll. The membrane is heated to a temperature above the melting point of the undercoating on the membrane, reducing it to a fluid liquid state in which the scales of metal float into an orderly arrangement one with another, in an overlapping, interlocking arrangement. This arrangement of the scales of metal presents such a tortuous passage for the passing of moisture through the coating from one side to the other that little if any moisture can penetrate the layer,

scales to settle into an orderly arrangement such as is described above. While this is the simplest way of carrying out my process, I find that I get of the scales from the helterbetter results by employing the two coatings as described in the preferred form of procedure.

In formulating my coating substance I prefer to use a high melting point treated rosin known in the trade as limed rosin, which has a melting point of about 240 F. Since this rosin is brittle I incorporate with it a relatively small proportion of non-brittle wax or gum such as petroleum wax or beeswax and a still smaller proportion of a plasticizer such as castor 011. As an example of the approximate proportions of these ingredients which I find satisfactory I give the following formula:-

Per cent Limed rosin 80 Petroleum wax or beeswax Castor oil 5 In the above description I have described the base coating as being of a resinous or waxy substance capable of being melted to a liquid of low viscosity, but I do not wish to be understood as limiting myself to resinous or waxy substance since there are other substances which at ordi- 3 nary temperatures may not properly be described the characteristic chiefly desired of the material used as the first or base coating.

Having described my invention and its method of operation fully and clearly so that one skilled in the art may utilize it, I now state what I believe to be new and novel and for which I pray that Letters Patent be granted.

I claim:-

1. The process of coating a membrane with a coating containing a metallic powder which consists in applying to the surface of the membrane a substance capable of melting to a liquid of low viscosity, applying thereupon a second coating containing metallic powder, and subjecting the composite membrane to a temperature sumcient to reduce the substance of the first coating to a liquid whereby the scales of metal constituting the metallic powder may settle into orderly arrangement in said liquid to produce a metallic coating of high luster.

2. The process of coating a membrane with a coating containing a metallic powder which consists in applying to the surface of the membrane a coating composed predominantly of resinous and waxy substance containing a metallic powand subjecting the thus coated membrane to a temperature suflicient to reduce the substance liquid whereby the scales of metal constituting the metallic powder arrangement in said liquid to produce a metallic coating of high luster.

ROBSON S. MOORE. 

